May 2020 Monthly Management

Preventing Lungworm Losses at Grass; Mid-Season Grassland Management

20 May 2020

Preventing Lungworm Losses at Grass

The lungworm parasite, Dictyocaulus viviparus, can cause severe respiratory disease in grazing cattle, and result in losses in productivity from even mildly affected animals. Prevention and early intervention are key to reducing potential losses from lungworm.

Lungworm disease is usually seen from July onwards and depending on the weather conditions over the later grazing season, can persist into autumn and early winter.

Warm, wet weather, helps the parasite to disperse onto the pasture from dung pats, so periods of high temperatures followed by heavy rain can indicate a forthcoming high risk period for susceptible cattle, as high numbers of larvae are suddenly released from the dung pats.

The problem for farmers, and vets, is that lungworm can be difficult to diagnose at an early stage and may not be spotted until a full-blown outbreak occurs.

Lungworm is no longer just a disease of youngstock. There is an increasing trend for adult cattle to be affected too. Vigilance is therefore vital during the high-risk periods of the year.

Clinical Signs of Lungworm Infections

Outbreaks of coughing in cattle should be investigated by a vet as soon as possible to allow early-intervention and minimise the long-term impact.

Other signs that can indicate lungworm infection include rapid loss of condition and sudden milk drop in lactating cows. These symptoms arise because cows will often spend less time grazing, and more time resting. Their water intake is also likely to be reduced.

Severely affected cattle will typically stand with head and neck extended in an ‘air hunger’ position as pictured below.

Figure 1: Severe lungworm infection in a first lactation cow (Scott, 2013)
Figure 1: Severe lungworm infection in a first lactation cow (Scott, 2013)

If one animal is infected, the whole group or herd will need treatment since all will have varying levels of lungworm burden, even if they are not exhibiting signs of disease.

Lifecycle of Lungworm (Dictyocaulus viviparus)
Lifecycle of Lungworm (Dictyocaulus viviparus)


After displaying initial signs of infection, we can confirm the presence of lungworm with faecal samples. Most wormers will treat lungworm burdens, however not every product will kill all life stages of the parasite. It is important that you speak to a vet before selecting a wormer so you can ensure you pick the most appropriate one. Young stock and growing cattle should be treated immediately with a wormer that quickly removes lungworm and prevents re- infection, to allow lungs to recover. All cattle in the group should be treated to ensure any sub-clinical cases are not missed. Overuse of wormers could limit exposure to the lungworm larvae to such an extent that cattle remain susceptible to infection.

A vet should assess severely affected individuals, as they may need additional treatment to treat pain, inflammation, and any secondary infection.

In dairy cows, a zero-milk withhold wormer such as Eprinex® Multi removes lungworm (as well as a range of other productivity-limiting parasites including Ostergagia ostertagi and Cooperia spp.) and prevents reinfection by lungworm for 28 days.

Work with your vet or animal health advisor to determine the most appropriate approach to lungworm control on your farm

Mid-Season Grassland Management

The main aim of mid-season grassland management is to manage fluctuations in grass growth, whilst also maintaining quality. Over the next 2-3 months grass growth rates will normally be over 60kgs/dm/day and even during this period there can be significant peaks and troughs in grass growth rates as can be seen in the graph below.

National Grass Growth Curve (Source: PastureBase Ireland)
National Grass Growth Curve (Source: PastureBase Ireland)

The ideal pre grazing yield is approximately 1400kg/dm/ha (7-9cm in height) for mid-season grazing. This corresponds to the 3-leaf stage of the plant when the performance of the plant and the cow eating the plant are both at the ideal position. This will feed the cow well and will assist in hitting the correct post grazing residual.

If grazing covers lower than 1200 kg/dm/ha, cow’s intakes and performance will suffer, and grass growth may drop off. When feeding higher covers than 1400 kg/dm/ha there will be a higher proportion of stem compared to leaf in the paddock reducing feed quality and making clean outs more difficult.

If clean outs are poor, then grass quality will be reduced in the next round. On the other side if cows are being forced to clean out strong paddocks it will result in:

  • Slowing the length of the rotation
  • Slower regrowths
  • Underfeeding the cow
  • Reduced milk output due to poorer quality grass
  • Lower milk protein content due to poorer quality

In periods of exceptional growth, any paddocks that are too strong for grazing should be taken out for surplus bales as soon as weather allows. There are a number of benefits associated with this:

  1. Reduce the length of the rotation to match the higher growth rates.
  2. The extra bonus of cleaning out the paddock where grazing could not possibly do and ensuring good quality grass for the next round of grazing.
  3. Excellent quality silage for buffer feeding during periods of feed deficits.

In periods of lower growth, grass allowance needs to be reduced and the rotation length may be extended by increasing supplementary feed.

Walking the Farm:

Grass growth can change fast during May and it is vital know to what is happening in terms of grass growth on the farm.

To do this you should walk the farm weekly. This will allow you to continually react to changes in growth.

Grass & Grazing

Grass and Grazing is a new section of the management notes where the grazing situation from a different Drinagh milk producer will be profiled each month.

John O'Mahony
This month’s feature is from John O’Mahony, Lower Kildee, Dunmanway.
Date 18/05/2020
Average farm cover 622 kg DM/ha
Yield (litres/cow) 27
Fat% 4.75%
Protein % 3.50%
Kgs Milk Solids / cow 2.29
Supplement fed(kg/cow) 2kg
Pre-grazing covers 1300
Days grass ahead 12 days

Growth for the last week was 66kg/DM/ha per day. Stocking rate is 3.17 LU/ha. Demand is 53kg/DM/ha. 2ha was cut for bales in early May and 10.70ha of the grazing platform is out for 1st cut silage which will be cut the first week of June. 2.60ha has been reseeded. The 3rd rotation started on the 5th May. The high EBI black and white spring calving herd are doing 2.29kg of milk solids and breeding started on 4th May.


Currently spreading 1.5 bags of 18-6-12 acre as soil Phosphorus levels are in need of being built up on the farm.